Physical Parameters of F and G-type Supergiants from uvbyβ Photometry and Gaia-DR2

We combine physical parameters derived from multi-color Strömgren-Crawford uvbyβ photometry with the second Gaia data release to exploit the properties of luminous F and G-type stars. Our sample contains more than 1000 F-G bright giants and supergiants of luminosity classes I, II and III. Employing uvbyβ-based individual reddening corrections, we calculate Gaia-based absolute magnitudes and evaluate the locus of these stars on various photometric diagrams. As an intermediate-band system in the visual spectral range, the uvbyβ photometry is quite resourceful in yielding reliable physical stellar parameters and refining the MK classification of the collated sample. Since these stars are very useful as extragalactic distance indicators, we also evaluate the current methodology for obtaining their photometry-based absolute magnitudes. Acknowledgments: This work is supported by an NSF grant AST-1516932.